This invention relates to a process for the production of a granulated protein gel which is readily rehydratable with water, and upon rehydration is suitable as a meat extender.
Vegetable protein products including soy flour, isolates and concentrates have become widely used and accepted food ingredients. Among the vegetable protein products which have been the most widely accepted are the textured vegetable protein materials which have gained wide acceptance as a meat extender. The extended meat products are comparable in nutrition and quality to the natural meat products.
A variety of textured vegetable protein materials and processes for the production have been proposed. Generally recognized as one of the first processes for texturization of protein was that described in U.S. Pat. No. 2,682,466. Edible protein filaments were produced by a spinning process similar to that for the spinning of textiles. The starting material for this texturization process was a protein isolate, which has the bulk of oil and carbohydrates removed to achieve a protein content of 90-95% by weight on a dry basis.
Although numerous texturization techniques have been proposed for materials of lower protein content such as soybean meal, soy flour or concentrates, the most widely used and commercially successful technique for the texturization of vegetable protein materials is the extrusion process described in U.S. Pat. No. 3,940,495. This process produces an expanded, meat simulating product which is capable of rehydration with water and upon rehydration is highly suitable as a meat extender. This type of extender was approved for use for the School Lunch Program by the U.S. Department of Agriculture, Food and Nutrition Service (FNS Notice 219) and since then has found wide usage in this program as well as by meat processors for the production of extended meat.
Other texturization processes too numerous to categorize have also been proposed following development of the extrusion process. These processes including the extrusion process, employ lower protein content vegetable protein materials as well as vegetable protein isolates. Some of these processes describe variations in the extrusion process described above in U.S. Pat. No. 3,940,495 for achieving differences in density or functionality of the textured product as well as an improvement or modification of the flavor or texture of the resultant product. Other processes have been directed to the production of non-expanded textured products, for example, an agglomerated protein material as described in U.S. Pat. No. 4,045,590 or an unpuffed proteinaceous extrudate as described in U.S. Pat. No. 3,498,794 and 3,968,268.
The non-expanded products generally exhibit poorer rehydration properties than the expanded materials, requiring longer times or extreme temperatures to achieve maximum rehydration capacity. Therefore, the non-expanded products are more suitable in canned products which employ significant amounts of water and use higher temperatures during retort cooking of the product. Hydration rate of the textured material is less of a factor in this type of product. The expanded products have therefore proven to be more successful as an extender in ground meat applications than the non-expanded products because of a better hydration rate as well as the formation of a mixture more nearly approximating that of natural meat.
In spite of the commercially developed nature of the textured vegetable protein industry, a continuing need exists for specific types of textured materials exhibiting specific functional properties for various food uses.
An object of the present invention is to present a process for the production of a textured vegetable protein material which has a high hydration capacity or ability to absorb water. It is also an object to provide a process for the production of a textured vegetable protein material which rehydrates rapidly with water under ambient conditions.
It is also an object to provide for the production of a textured protein material from a vegetable protein isolate which exhibits the above rehydration characteristics and blends well with ground meat to provide a mixture comparable to the natural meat.
It is a further object to provide a process for the production of the above material which is convenient and reliable to practice on a commercial basis.